[compiler-rt] r337170 - [cfi] Don't pass a uint16_t to memset. Make sure the 16-bit constant is appropriate for us.

[Filipe Cabecinhas via llvm-commits]

Sorry. Fixing!

 Filipe

On Mon, 16 Jul 2018 at 14:57, Benjamin Kramer <benny.kra at gmail.com> wrote:

>
>
> On Mon, Jul 16, 2018 at 3:46 PM Filipe Cabecinhas via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: filcab
>> Date: Mon Jul 16 06:41:54 2018
>> New Revision: 337170
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=337170&view=rev
>> Log:
>> [cfi] Don't pass a uint16_t to memset. Make sure the 16-bit constant is
>> appropriate for us.
>>
>> Reviewers: eugenis, pcc, kcc
>>
>> Subscribers: delcypher, #sanitizers, llvm-commits
>>
>> Differential Revision: https://reviews.llvm.org/D49252
>>
>> Modified:
>>     compiler-rt/trunk/lib/cfi/cfi.cc
>>
>> Modified: compiler-rt/trunk/lib/cfi/cfi.cc
>> URL:
>> http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/cfi/cfi.cc?rev=337170&r1=337169&r2=337170&view=diff
>>
>> ==============================================================================
>> --- compiler-rt/trunk/lib/cfi/cfi.cc (original)
>> +++ compiler-rt/trunk/lib/cfi/cfi.cc Mon Jul 16 06:41:54 2018
>> @@ -132,7 +132,10 @@ void ShadowBuilder::Start() {
>>  void ShadowBuilder::AddUnchecked(uptr begin, uptr end) {
>>    uint16_t *shadow_begin = MemToShadow(begin, shadow_);
>>    uint16_t *shadow_end = MemToShadow(end - 1, shadow_) + 1;
>> -  memset(shadow_begin, kUncheckedShadow,
>> +  // memset takes a byte, so our unchecked shadow value requires both
>> bytes to
>> +  // be the same. Make sure we're ok during compilation.
>> +  static_assert(kUncheckedShadow & 0xff == ((kUncheckedShadow >> 8) &
>> 0xff));
>>
>
> llvm/projects/compiler-rt/lib/cfi/cfi.cc:137:34: error: & has lower
> precedence than ==; == will be evaluated first [-Werror,-Wparentheses]
>   static_assert(kUncheckedShadow & 0xff == ((kUncheckedShadow >> 8) &
> 0xff));
>                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> llvm/projects/compiler-rt/lib/cfi/cfi.cc:137:34: note: place parentheses
> around the '==' expression to silence this warning
>   static_assert(kUncheckedShadow & 0xff == ((kUncheckedShadow >> 8) &
> 0xff));
>                                  ^
>                                    (
>  )
> llvm/projects/compiler-rt/lib/cfi/cfi.cc:137:34: note: place parentheses
> around the & expression to evaluate it first
>   static_assert(kUncheckedShadow & 0xff == ((kUncheckedShadow >> 8) &
> 0xff));
>                                  ^
>                 (                      )
> llvm/projects/compiler-rt/lib/cfi/cfi.cc:137:76: error: static_assert with
> no message is a C++17 extension [-Werror,-Wc++17-extensions]
>   static_assert(kUncheckedShadow & 0xff == ((kUncheckedShadow >> 8) &
> 0xff));
>
>  ^
>
>  , ""
>
>
>> +  memset(shadow_begin, kUncheckedShadow & 0xff,
>>           (shadow_end - shadow_begin) * sizeof(*shadow_begin));
>>  }
>>
>>
>>
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>>
>
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